This invention pertains to a thin cathode-ray tube.
A standard cathode-ray tube comprises a faceplate panel with a cathodoluminescent screen, a funnel-shaped back section having a neck, and a mount containing an electron gun. The back section typically is sealed to the faceplate panel in a high-temperature oven using a glass frit before the mount is sealed to the neck of the funnel-shaped back section. The mount is sealed to the neck of the back section by a flame-sealing apparatus which necessarily requires the protruding-shaped neck in order to effectively apply a localized torch of the flame-sealing apparatus.
Efforts to decrease the overall depth of such tubes have resulted in cathode-ray tubes designed so that the protruding-shaped neck is geometrically repositioned from the center of the funnel-shaped back section to a side-mounted location whereat the electron gun emits electrons having an initial direction of travel substantially parallel to the cathodoluminescent screen. An example of such a tube is described in U.S. Pat. No. 4,374,343 issued to me on Feb. 15, 1983, and assigned to RCA Corporation. However, it is difficult to effectively deflect the electron beam from such a side-mounted gun so that it scans the entire screen while simultaneously focusing the beam and bending it toward the screen.
In order to improve the focusing capability of the electron beam while simultaneously achieving a thinner cathode-ray tube, it is desirable to position the mount containing the electron gun closer to the screen while keeping the gun pointed in a direction orthogonal to the center of the screen. The geometrical considerations for the design of such a tube require a differently shaped back section which may not include a neck, thereby precluding the feasibility of utilizing a mount-sealing step wherein a torch is applied to the neck. The present invention achieves a thinner cathode-ray tube, having a substantially symmetrical design, wherein the mount of the tube is frit sealed to the back section thereof.